This invention relates generally to swage machines and more particularly to collars and dies used to retain tubes in such machines during the swaging process.
Swaging involves the tapering of a rod or tube, such as by forging, hammering, or squeezing. It may also involve the joining together of two components by similar manipulation. For example, a fitting, just as a coupling, may be joined to the exterior of a tube by any of the operations of forging, hammering or squeezing. In general, the fitting is placed on the outside of the rod or tube and then swaged into place, preferably substantially where located. Swaging is a common practice for applying fittings to tubes. A plurality of tubes may be joined together by way of their fitting connections that have been swaged to either or both ends of the tubes.
Although swaging may be performed manually, swage machines are used to automate and facilitate the process of swaging a fitting to a tube. A wide array of swaging machines is available. Most include means for retaining one or more dies. A die retains the fitting and tube in place during the swaging process. With the fitting and tube in place in the die, pressure is applied to the exterior of the fitting where it is in contact with the exterior of the tube. This is achieved either by rotating the piece, tube, rod, or the like, to be worked or by rotating swaging devices about the piece that remains in a fixed position. The pressure applied to a tube work piece may alternatively be made from the interior of the tube by way of an expander. This is referred to as internal roller swaging.
In most instances, the fitting is larger than the tube. Given the proximity of the two within a die or set of dies, it is necessary to include means to capture the tube within the die to keep it fixed in place during the swaging process. Such means is a tight-fit annular insert that is placed around the tube and resides in a recess in the die. The insert is generally made of a non-metallic material, such as nylon. The nylon insert wedges the tube in place within the die. For internal roller swaging, a set of opposing die halves is used to position the fitting and tube. Each half includes a half-annular nylon insert. The tube and fitting are placed in one of the halves and then clamped in place when the second die half is mated to the first.
It has been determined that the nylon insert is inadequate to retain the tube in place during the swaging process. Specifically, because the insert is made of a viscoelastic material, it often fails to provide adequate clamping force during the rigorous swaging process. As a result, the tube rotates and/or moves axially during the process. In addition, the amount of clamping force associated with the die set is dependent on individual die tolerances and die wear when using the nylon inserts. It is therefore often necessary for an operator to hold the tube in place to prevent rotation and axial movement. This limits the efficiency of the automated swaging process, minmizes the operator""s ability to perform other tasks, and increases the yield of defective parts. Therefore, what is needed is a die and die-to-tube interface arrangement that retain the tube and fitting in place with certainty during swaging.
The above-mentioned need is met by the present invention, which provides a die and collar assembly for retaining a tube and its fitting in place in a swage machine. The assembly includes a collar releasably placeable on the work piece and a die insertable into the swage machine. The die includes a work piece slot and a collar recess in a die face of the die. The collar recess is configured to retain the collar that in turn is coupled about the work piece. The collar includes a first clamping section and a second clamping section that are connected together during the swaging process. For curved work pieces, the collar includes in one of its faces a chamfered section to accommodate the curved portion of the work piece. The collar recess and the collar may be of hexagonal shape. When a fitting is to be swaged to the work piece, a fitting recess is formed in the die face. In addition, a dummy fitting may be used to fix the position of the collar on the work piece before swaging a final fitting.
The present invention and its advantages over the prior art will become apparent upon reading the following detailed description and the appended claims with reference to the accompanying drawings.